88 A Manual of Veterinary Physiology . 



ferment on fibrinogen and serum globulin is held to be 

 against the weight of evidence, which points to the 

 presence of serum globulin as being unnecessary to coagu- 

 lation. 



The presence of neutral salts is necessary for the con- 

 version by means of the ferment of fibrinogen into fibrin ; 

 no fibrin can be produced in their absence. Calcium 

 sulphate appears to be the essential salt. 



The Theories of Coagulation are very diverse, whilst 

 Schmidt, as mentioned above, considered that the presence 

 of fibrinogen, serum globulin, and the fibrin ferment, were 

 all necessary to the process of clotting, Hammarsten 

 considered that the globulin was unnecessary. Wool- 

 dridge believed that a substance found in the white 

 corpuscles, lecithin, diffused into the plasma and produced 

 clotting. In all cases, however, it was recognised that the 

 salts of the blood were absolutely essential to the process. 



The term ' ferment ' in connection with] fibrin ferment, is 

 used more as a convenient expression than as an actual 

 statement of its action ; it is considered doubtful whether 

 it ' splits up ' fibrinogen into fibrin, and this it would pro- 

 bably do if a ferment. 



It appears to be quite clear that fibrinogen and the 

 fibrin ferment are the important factors in coagulation, 

 for if a solution of fibrinogen be prepared in a pure con- 

 dition, it will clot on the addition of the ferment, even 

 though serum globulin be absent, the fibrinogen by itself 

 being non-coagulable ; conversely, if fibrinogen be removed 

 from a fluid the latter will not coagulate even on the 

 addition of the ferment. Certain pathological fluids, serum 

 from the chest, etc., may be made to coagulate on the 

 addition of a little washed blood clot, which contains the 

 ferment in considerable quantities. Experiments made by 

 injecting into the vessels of animals the active fibrin 

 ferment, do not lead to coagulation of the blood in the 

 vessels as we might suppose ; the ferment is either 

 destroyed, or else fibrinogen is not present; the former is 

 the most likely. 



